The present invention relates to flexible shaft drive transmissions and more particularly to flexible shaft drive transmissions that are used to transmit drive between relatively small motors and hand held tools or other driven implements that are moved relative to the drive motor during use.
Flexible shaft drive transmissions serve to drive hand held tools, etc., from remote stationary motors so that the tool can be manipulated and moved around relative to the motor. Power operated rotary knives used in the meat packing industry are exemplary of such tools. These knives are often connected to overhead stationary motors via flexible drive transmissions so that workers using the knives are free to manipulate the knives while slicing meat being processed.
The flexible drive transmissions typically comprise a flexible drive shaft formed from a cable-like length of tightly wound wires, and a flexible casing that loosely surrounds the drive shaft. The drive shaft rotates within the casing, which is fixed against rotation, to transmit drive from the motor to the knife. As the knife is operated and the drive transmission is flexed, the drive shaft may contact the surrounding casing and also whip around within the casing, particularly when the knife requires relatively high torque and the drive transmission is relatively tightly curved. The casing contains a lubricant that reduces friction and shaft wear. The lubricant is edible so that, should it leak from the drive transmission, it does not contaminate the meat being processed. When the knife is operated without a proper supply of lubricant the drive shaft wears excessively and tends to whip around in the casing more than usual. Consequently the entire drive transmission vibrates. The worker using the knife can experience increasing discomfort as vibrations intensify over time.
In order to maximize the drive transmission life and reduce worker discomfort, drive transmission manufacturers have recommended frequent maintenance and drive shaft lubrication. The typical maintenance operation involves pulling the drive shaft out of the casing and wiping the lubricating grease off. A swab-like cleaning tool-such as a gun cleaning rod and swab-is then forced through the casing to scrub out residual lubricant and particulate material. Fresh lubricant is applied, and the drive shaft and casing are reassembled. Ideally this procedure is followed once or more per week depending on knife usage. But oftentimes proper maintenance procedures are practiced haphazardly, if at all.
There are various reasons why flexible drive transmissions are not properly maintained. In some facilities, where the knife operator must perform. maintenance, the time required for maintenance reduces productivity to an extent that is unacceptable to the operator. Moreover, the maintenance tasks themselves are not easily performed. Consequently, the average flexible drive transmission has a useful life of from 6 to 16 weeks depending, at least partly, on the frequency and thoroughness of the maintenance performed.
The present invention provides a new and improved flexible shaft drive transmission wherein the drive shaft is permanently fixed within the casing, the casing and drive shaft are sealed against leakage of lubricant from the transmission, and the need for periodic maintenance is obviated.
According to the invention a maintenance free flexible shaft drive transmission is provided that comprises a flexible drive shaft assembly having a first end connectable to a drive motor and a second end connectable to a driven implement, a tubular casing surrounding and coaxial with the drive shaft assembly, a lubricant disposed within the casing, and a lubricant seal for blocking leakage of lubricant from the second drive shaft assembly end.
The drive shaft assembly comprises a flexible elongated drive transmitting shaft member, a first drive coupling fixed to the drive transmitting shaft member at the first end, and a second drive coupling fixed to the drive transmitting shaft member at the second end.
The casing supports the drive shaft assembly for rotation generally about the longitudinal axis of the drive shaft assembly relative to the casing. The casing comprises a tubular flexible conduit loosely surrounding the drive transmitting shaft member, a first end fitting fixed to the conduit adjacent the first drive shaft assembly end and a second end fitting fixed to the conduit at the second drive shaft assembly end. The first end fitting comprises first and second fitting members that are fixed together and permanently secure the first drive coupling against axial movement relative to the casing to preclude removal of the drive shaft assembly from the casing. The first and second fitting members are constructed for enabling relative rotation between the drive coupling and the first end fitting;
The lubricant seal is disposed between the second end fitting and the drive shaft assembly second end for blocking leakage of lubricant from the casing as the casing and drive shaft assembly rotate and shift axially relative to each other.
Additional features and advantages will become apparent from the following description of an illustrated embodiment made with reference to the accompanying drawings which from part of the specification and wherein: